If you take other potential candidates at their word when they say they're not running -- and assume all-but-declared candidates will ultimately get in -- Daniels' announcement ends a period of extended uncertainty in the GOP field of would-be challengers to President Obama.

That means a chance for some of the folks who are running to get second -- or, in some cases, first -- looks from Republican activists and primary voters.

Other big names could still get in, and a boomlet for one or more of the non-candidates is all but inevitable. But most of those possible entries -- Republican superstars such as former Alaska Gov. Sarah Palin, New Jersey Gov. Chris Christie and Texas Gov. Rick Perry -- would be more likely to make a move in the fall than the spring or summer.

So for now, with former Gov. Mitt Romney, R-Mass., looming as the putative front-runner, the race will be on for a Romney alternative to emerge.

Two candidates, by dint of positioning and timing, appear poised to fill the gap left by Daniels and the other big names to bow out before him.

Former Gov. Tim Pawlenty, R-Minn., draws a lucky hand by dint of timing: He is set to announce his candidacy Monday. His profile -- a two-term battleground state governor with strong ties to social conservatives -- matches up well against Romney.

Pawlenty is signaling an aggressive play in the Iowa caucuses, where Romney came up short in 2008, and where Mike Huckabee's non-candidacy has opened up running room.

"You got to win one of them pretty quickly in the process," Pawlenty told Huckabee Saturday on his Fox News program. "And Iowa of course is first up."

Then there's Huntsman, barely three weeks after wrapping up his service as Obama's ambassador to China and already acting like a candidate with visits to early-voting states. He's in the middle of a testing-the-waters trip through New Hampshire, almost certainly a must-win state for Romney in the primaries.

For all his flaws as a candidate, Huntsman, the former governor of Utah, has the advantage of being the candidate about whom perhaps the least is known, during a period when Republicans are looking for fresh faces.

The tumultuous last few weeks in the field have been marked not just by the non-candidacies of Daniels, Huckabee, Donald Trump and Haley Barbour, but by the rocky debut on the trail by former House Speaker Newt Gingrich.

Gingrich flubbed a question about House Budget Chairman Paul Ryan's Medicare plan last weekend. He spent the week trying to clean up a mess that managed to sap his support among both the GOP establishment and tea party activists.

Today he answered questions for the first time about a line of credit of more than $250,000 he owed to Tiffany's in the mid-2000s. He's still not saying what he purchased, but his saying on CBS' "Face the Nation" that he's "very frugal" and lives debt-free isn't going to stop yet another damaging storyline from weighing him down.

That leaves even more room for other candidates. Rep. Michele Bachmann, R-Minn., is a near-certainty to get in the race, with a strong fundraising base and social-conservative profile that could make her a major player in Iowa -- and a drag on her fellow Minnesotan, Pawlenty.

Even former pizza magnate Herman Cain, who announced his candidacy Saturday, could make some noise in the campaign's early going. Cain got an unexpected boost from no less a voice than Sarah Palin's over the weekend.

"I get kind of excited thinking about what it is he has to offer in the discourse and the debate," Palin told Fox Saturday.

This all leaves Palin herself -- who allowed last week that she does have the "fire in my belly" to run -- atop a list of still-possible candidates.

A Palin candidacy would scramble everything about the race. But she has the flexibility of an automatic fundraising machine and media exposure, so she's not under pressure to declare any time soon.

Another potential candidate, House Budget Chairman Paul Ryan, R-Wis., affirmed today that he's still committed to not running. Other potential candidates -- such as Christie, Perry, and former Florida Gov. Jeb Bush -- have similarly left no doubt that they're not running, whether their boosters want to believe them or not.

That all may change. But for now, while several doors remain wide open, no new major candidates appear ready to walk through them.

That means Republicans are going to have to be content with what they've got, for at least a little while. What remains of the field will be happy for the attention.